Hollow Carbon Fibers Research Articles

Emerging contaminants removal through fluorine-doped carbon hollow fiber microfiltration membrane based on metal-free electro-Fenton

The emerging contaminants with high toxicity and bioaccumulation potentially threaten to human health, which was difficult removed by traditional biological treatment or membrane separation. In view of this, a novel type of fluorine (F)-doped carbon hollow fiber microfiltration membrane was prepared for realizing emerging contaminants removal through metal-free electro-Fenton. Herein, polyaniline (PANI) was used as a precursor for preparation of porous carbon membrane. The graphitic N and pyridinic N on porous carbon were used as the active sites for H2O2 production and its further activation to ·OH, which realized metal-free electro-Fenton reaction. According to the results, the carbon nanotubes with F-PANI at the ratio of 1:1 and calcination temperature at 300°C endowed the membrane moderate resistance and pure water permeability of 430 Ω and 48.51 L/(m2·h·bar), respectively. Importantly, the intensity of ·OH generation was further significant enhanced by introducing C-F bonding into the membrane. Therefore, the bisphenol A (BPA), sulfamethoxazole (SMZ) and atrazine (ATZ) removal rates were 92.63%, 38.47% and 27.05%, respectively. For control group without bias, the removal rates of above contaminants were 0% removal rates. Moreover, the membrane permeate loss by filtrating BPA, SMZ and ATZ were 0.13, 0.15 and 0.05, which were 0.20, 0.24 and 0.21 for control group.

Ultraselective carbon hollow fiber membrane for H2 extraction from blended natural gas

Blending hydrogen into natural gas (H2NG) pipelines is a feasible solution for low-cost hydrogen delivery while purifying H2 at end-use remains challenging due to its high pressure and low H2 concentration. Herein, biomass-derived carbon hollow fiber membranes (CHFMs) with ultrahigh H2/CH4 separation factor of 4149.0 under a simulated H2NG (10 mol% H2/90 mol% CH4) at 30 bar were reported, and the separation performance maintained within 150 h in a dynamic durability test. Furthermore, the CHFMs showed good stability under fluctuating temperature feeds (up to 100 °C). To evaluate the feasibility of the CHFMs for H2 extraction from H2NG, a three-stage membrane system was designed based on the mixed gas separation performances. It suggested that 99.99 mol% H2 can be achieved with a 90 % recovery, and the specific H2 purification cost was 0.245 $/Nm3 for a 1.8 × 105 Nm3/h production scale, which provides the possibility of hydrogen extraction from H2NG pipelines.

A Dual-Carbon Potassium-Ion Capacitor Enabled by Hollow Carbon Fibrous Electrodes with Reduced Graphitization.

The large size of K+ ions (1.38 Å) sets a challenge in achieving high kinetics and long lifespan of potassium storage devices. Here, a fibrous ZrO2 membrane is utilized as a reactive template to construct a dual-carbon K-ion capacitor. Unlike graphite, ZrO2-catalyzed graphitic carbon presents a relatively disordered layer arrangement with an expanded interlayer spacing of 0.378nm to accommodate K+ insertion/extraction. Pyridine-derived nitrogen sites can locally store K-ions without disrupting the formation of stage-1 graphite intercalation compounds (GICs). Consequently, N-doped hollow graphitic carbon fiber achieves a K+-storage capacity (primarily below 1V), which is 1.5 time that of commercial graphite. Potassium-ion hybrid capacitors are assembled using the hollow carbon fiber electrodes and the ZrO2 nanofiber membrane as the separator. The capacitor exhibits a high power of 40 000 W kg-1, full charge in 8.5 s, 93% capacity retention after 5000 cycles at 2 A g-1, and a low self-discharge rate of 8.6mV h-1. The scalability and high performance of the lattice-expanded tubular carbon electrodes underscores may advance the practical potassium-ion capacitors.

MOF derivatives anchored to multichannel hollow carbon fibers with gradient structures for corrosion resistance and efficient electromagnetic wave absorption

With the rapid development of 5G technology and the interconnection of industrial production, electromagnetic pollution has become a serious problem. Achieving lightweight and controllable loads of absorbers while obtaining corrosion-resistant absorbers with high electromagnetic response properties is still considered a huge challenge. In this work, carbon fiber with a multichannel hollow structure is obtained by PAN/PS hybrid electrospinning and subsequent high-temperature roasting process. The spatial structure inside the carbon fiber plays an active role in optimizing the impedance matching characteristics of the absorber. In addition, bimetallic metal-organic frameworks (MOFs) derivatives are obtained by a precisely controlled ion exchange as well as a high-temperature gas-phase selenization process. The resulting introduction of a non-homogeneous interface induces interfacial polarization and improves the absorption behavior of the absorber. The analysis of the experimental results shows that the electromagnetic wave (EMW) absorption performance can be effectively enhanced due to the mechanisms of interface polarization and dipole polarization. The prepared NiSe/ZnSe/MHCFs composite can obtain excellent EMW absorption properties in C, X, and Ku bands by adjusting the thickness. Structural design and component modulation play a crucial role in realizing the strong absorption and wide bandwidth of the absorber. Radar cross-section calculations indicate that NiSe/ZnSe/MHCFs have tremendous potential in practical military stealth technology. And the prepared composite coating can provide periodic corrosion resistance to Q235 steel sheet when dealing with complex and extreme environments.

Design of an active wing-folding biomimetic flapping-wing air vehicle

In nature, birds and bats dynamically alter their wing shapes to suit various flight environments and tasks. This paper focuses on the design and validation of a biomimetic flapping-wing aerial vehicle, named FlexiWing, which features a unique mechanism for active wing deformation. This mechanism allows the wings to adjust their shapes flexibly in response to flight demands, significantly enhancing attitude control and maneuverability.’ ‘This study began with an in-depth exploration of biomimetic principles, focusing particularly on how birds and bats achieve precise control during flight through active wing deformation. Subsequently, we present a detailed account of the design and fabrication process of the active folding biomimetic flapping-wing aerial vehicle, including the design of mechanical mechanisms and material selection. Utilizing lightweight nylon materials and hollow carbon fiber rods, we successfully constructed a mechanically foldable wing structure. To achieve precise control over the aircraft’s movement, an embedded control system was designed, comprising an onboard embedded flight controller and ground-based equipment. The onboard controller uses a high-performance ESP32-C3 processor and a JY901 inertial measurement unit to acquire real-time attitude information of the aircraft. The control system incorporates Wi-Fi communication technology, enabling operators to send commands via a remote control or personal computer to manage flight modes and attitudes. Ultimately, a series of flight experiments were conducted to validate the performance of FlexiWing. The results demonstrate that FlexiWing exhibits remarkable maneuverability and stability, capable of achieving high-precision attitude control through active wing folding, making it adaptable to complex environments and tasks.’

Curvature-induced strain to realize differential lithiophilicity for selective lithium deposition and stable lithium anode

Regulating the lithiophilicity of three-dimensional (3D) lithium hosts is crucial for improving lithium deposition and suppressing dendrite growth. However, previous research has mainly focused on varying lithiophilic components, and the impact of geometric structures induced strain remains poorly understood. Herein, we present a novel curvature-induced strain engineering approach to regulate lithiophilicity and deposition kinetics of lithium in lightweight 3D tubular carbon hosts. A hollow carbon fiber with bilateral growth of MnO2 nanosheet arrays both inside and outside the tubes (MnO2@HCFC) have been successfully synthesized. Theoretical calculations and experiments confirm that the MnO2 layers inside and outside the hollow carbon fiber tube undergo compressive and tensile strain, respectively. The curvatures induced strain modifies the O2p band center of the lithiophilic MnO2 layer, enabling the regulation of lithiophilicity and preferential and uniform lithium deposition within the carbon fiber tubes. The MnO2@HCFC framework exhibits excellent lithium affinity and uniform Li+ flux distribution, as evidenced by visualization techniques and COMSOL simulations, enabling dendrite-free lithium deposition. The Li-MnO2@HCFC||LiCoO2 full cell retains 85.7 % of its capacity after 400 cycles at 0.5 C with a high LiCoO2 loading of 10.3 mg cm-2. The optimized lithium anode pouch cell exhibits robust cycle stability under harsh conditions. This work offers new insight into the design of 3D lithium hosts to enhance the performance of lithium anodes through curvature-induced strain engineering.

Immobilization and Catalytic Conversion of Polysulfide by In-Situ Generated Nickel in Hollow Carbon Fibers for High-Rate Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered promising energy-storage systems because of their high theoretical energy density, low cost, and eco-friendliness. However, problems such as the shuttle effect can result in the loss of active materials, poor cyclability, and rapid capacity degradation. The utilization of a structural configuration that enhances electrochemical performance via dual adsorption-catalysis strategies can overcome the limitations of Li-S batteries. In this study, an integrated interlayer structure, in which hollow carbon fibers (HCFs) were modified with in-situ-generated Ni nanoparticles, was prepared by scalable one-step carbonization. Highly hierarchically porous HCFs act as the carbon skeleton and provide a continuous three-dimensional conductive network that enhances ion/electron diffusion. Ni nanoparticles with superior anchoring and catalytic abilities can prevent the shuttle effect and increase the conversion rate, thereby promoting the electrochemical performance. This synergistic effect resulted in a high capacity retention of 582 mAh g-1 at 1 C after 100 cycles, providing an excellent rate capability of up to 3 C. The novel structure, wherein Ni nanoparticles are embedded in cotton-tissue-derived HCFs, provides a new avenue for enhancing electrochemical performance at high C rates. This results in a low-cost, sustainable, and high-performance hybrid material for the development of practical Li-S batteries.

Tailored Magnetic Spatial Confinement with Enhanced Polarization and Magnetic Response for Electromagnetic Wave Absorption.

For materials with coexisting phases, the transition from a random to an ordered distribution of materials often generates new mechanisms. Although the magnetic confinement effect has improved the electromagnetic (EM) performance, the transition from random to ordered magnetic confinement positions remains a synthetic challenge, and the underlying mechanisms are still unclear. Herein, precise control of magnetic nanoparticles is achieved through a spatial confinement growth strategy, preparing five different modalities of magnetic confined carbon fiber materials, effectively inhibiting magnetic agglomeration. Systematic studies have shown that the magnetic confinement network can refine CoNi NPs size and enhance strong magnetic coupling interactions. Compared to CoNi@HCNFs on the hollow carbon fibers (HCNFs) outer surface, HCNFs@CoNi constructed on the inner surface induce stronger spatial charge polarization relaxation at the interface and exhibit stronger magnetic coupling interactions at the inner surface due to the high-density magnetic coupling units at the micro/nanoscale, thereby respectively enhancing dielectric and magnetic losses. Remarkably, they achieve a minimum reflection loss (RLmin) of -64.54dB and an absorption bandwidth of 5.60GHz at a thickness of 1.77mm. This work reveals the microscale mechanism of magnetic confinement-induced different polarization relaxation and magnetic response, providing a new strategy for designing magnetic materials.

Precise Helium Sieving from Hydrogen Using Fluorine‐Decorated Carbon Hollow Fiber Membranes

AbstractSeparating helium (He) and hydrogen (H2), two gases that are extremely similar in molecular size and condensation properties, presents a formidable challenge in the helium industry. The development of membranes capable of precisely differentiating between these gases is crucial for achieving large‐scale, energy‐efficient He/H2 separation. However, the limited selectivity of current membranes has hindered their practical application. In this study, we propose a novel approach to overcome this challenge by engineering submicroporous membranes through the fluorination of partially carbonized hollow fibers. We demonstrate that the fluorine substitution on the inner rim of the micropore walls within the carbon hollow fibers enables tunability of the microporous architecture. Furthermore, it enhances interactions between H2 molecules and the micropore walls through the polarization and hydrogen bonding induced by C−F bonds, resulting in simultaneous improvements in both He/H2 diffusivity and solubility selectivities. The fluorinated HFM‐550‐F‐1 min membrane exhibits exceptional mixed‐gas separation performance, with a binary mixed‐gas He/H2 selectivity of 10.5 and a ternary mixed‐gas He/(H2+CO2) selectivity of 20.8, at 40 bar feed pressure and 35 °C, surpassing all previously reported polymer‐based gas separation membranes, and remarkable plasticization resistance and long‐term continuous stability over 30 days.

Precise Helium Sieving from Hydrogen Using Fluorine-Decorated Carbon Hollow Fiber Membranes.

Separating helium (He) and hydrogen (H2), two gases that are extremely similar in molecular size and condensation properties, presents a formidable challenge in the helium industry. The development of membranes capable of precisely differentiating between these gases is crucial for achieving large-scale, energy-efficient He/H2 separation. However, the limited selectivity of current membranes has hindered their practical application. In this study, we propose a novel approach to overcome this challenge by engineering submicroporous membranes through the fluorination of partially carbonized hollow fibers. We demonstrate that the fluorine substitution on the inner rim of the micropore walls within the carbon hollow fibers enables tunability of the microporous architecture. Furthermore, it enhances interactions between H2 molecules and the micropore walls through the polarization and hydrogen bonding induced by C-F bonds, resulting in simultaneous improvements in both He/H2 diffusivity and solubility selectivities. The fluorinated HFM-550-F-1 min membrane exhibits exceptional mixed-gas separation performance, with a binary mixed-gas He/H2 selectivity of 10.5 and a ternary mixed-gas He/(H2+CO2) selectivity of 20.8, at 40 bar feed pressure and 35 °C, surpassing all previously reported polymer-based gas separation membranes, and remarkable plasticization resistance and long-term continuous stability over 30 days.

Hollow carbon fiber wrapped by regular rGO wave-like folds for efficient solar driven interfacial water steam generation

Efficient seawater desalination is an effective way to solve the shortages of fresh water and energy but with limitations of the low fresh water production rate and high cost. Here, a hollow carbon fiber (HCF) wrapped by regular reduced graphene oxide (rGO) wave-like folds (rGO@HCF) is prepared on account of the differences in thermal shrinkage performance between graphene oxide (GO) and willow catkins fiber. Under one sun irradiation (1 kW m−2), the dry and wet surface temperature of the resulting evaporator reached up to 119.1 °C and 61.7 °C, respectively, and the water steam production rate reached 3.42 kg m−2 h−1. Also, for the outdoor experiment, the rGO@HCF exhibits good evaporator performance which reach up 27.8 kg m−2 day−1. Additionally, rGO@HCF also shows good seawater desalination performance and excellent durability for longtime work. DSC results indicate that the evaporation enthalpy of bulk water and adsorbed water decreased from 2503.92 to 1020.54 J g−1. The excellent evaporating performance is mainly attributed to the regular wave-like microstructure surface of the HCF, which can enhance the light absorption, reduced the vaporization enthalpy of the adsorption water. The findings not only introduce a novel approach for agricultural utilization, but also establish a crucial theoretical foundation for the design of regular wave-like microstructures.

Intermediate layer free PVDF evolved CMS on ceramic hollow fiber membrane for CO2 capture

The use of carbonized polymers has ushered in a new class of materials with profound implications for the gas separation industry. This study explored the transformation of polyvinylidene fluoride (PVDF) into microporous carbon structures coated onto ceramic substrates, enabling in situ growth of carbon molecular sieve (CMS) materials over hollow fibers. This material featured more robust CMS membranes than alumina and demonstrated exceptional capability in vital gas separations, particularly for CO2/CH4. This novel approach increased the selectivity for gases and exhibited remarkable aging resilience, so the material is a compelling candidate for high-performance gas separations. Furthermore, after 31 days, the weathered carbon dioxide membrane exhibited a slight permeability drift from 234.88 barrers to 195.35 barrers, while the CO2/CH4 ratio increased from 24.21 to 57.14, surpassing the Robeson 2008 upper bound. The PVDF-derived supported hollow fiber carbon membranes provide a blueprint for designing membranes for carbon capture. With the high packing density of the hollow fiber membrane and improved mechanical strength of the supported carbon membrane, this approach overcame the high fabrication costs and brittleness of other carbon membranes. In addition, the entire process for preparation of the PVDF carbon films is easily scaled up and has great potential for future practical application.

CeO2/Co heterostructure encapsulated in hollow necklace-like carbon fiber as an advanced host material for high-performance lithium-sulfur batteries

The shuttle effect of lithium polysulfides (LiPSs) and the sluggish reaction kinetics of LiPSs conversion pose serious challenges to the commercial feasibility of lithium-sulfur (Li-S) batteries. To address these obstacles, herein, we construct CeO2/Co heterostructures in hollow necklace-like carbon fibers (CeO2/Co-CNFs) as the cathode host material for Li-S batteries. The specific surface area of fibers is significantly enhanced by using a template, thereby promoting the utilization efficiency of sulfur. Meanwhile, CeO2/Co-CNFs show strong conductivity, effective adsorption to LiPSs, and robust catalytic activity for LiPSs conversion. As a result, the Li-S battery with CeO2/Co-CNFs displays 961 mAh g−1 at 0.2 C, with an 86 % capacity retention rate after 100 cycles. At 2.0 C current density, the composite cathode maintains an initial discharge capacity of 782 mAh g−1, with a mere 0.044 % capacity loss per cycle. Furthermore, in situations with limited electrolytes, high sulfur loading, and high areal mass loading, the composite cathode can provide a high areal capacity of 6.2 mg cm−2 over 100 cycles. This work provides a useful approach for investigating high-performance Li-S battery cathodes.

Investigating Hydrocarbon Gases Permeability Through Hollow Fiber Hybrid Carbon Membrane

Hydrocarbon separation from natural gases is a critical procedure in the chemical and petrochemical industries. This study used hollow fiber carbon membranes (HFCMs) made from a commercially available co-polyimide, P84, with zeolite-carbon composite (ZCC) as a filler to separate light hydrocarbons like CH4/C3H8 and CH4/C2H6. The Arrhenius technique was used to evaluate the effects of temperature fluctuations (298, 323, and 373 K) on the membrane. X-ray diffraction exhibited a characteristic graphite peak at 2θ ~ 44°, indicating the creation of an effective carbon membrane. SEM investigation revealed the compactness of both pristine and hybrid carbon membrane structures. The operating temperature has a significant influence on the gas penetration through the membrane when evaluating gas permeation. The hybrid carbon membrane has the highest permeability for CH4, C2H6, and C3H8 at 373 K. (81.86, 61.82, and 58.28 Barrer, respectively). The carbon membrane also showed greatest selectivity for CH4/C3H8 and CH4/C2H6 at 323 K (2.24 and 2.04, respectively). Adsorption and surface diffusion were the membrane's transport mechanisms. By adding filler to the membrane, the gas permeability was temperature dependent.

Designed MoSe2 modified multi-layer hollow carbon fiber composite material achieves tunable electromagnetic wave absorption in the X and Ku bands

As a substitute for graphene-based carbon materials, carbon fiber (CF) based absorbing materials have enormous application prospects. Effective improvements have been made in solving the problems of heavy quality and complex preparation processes of ordinary absorbing materials. In order to obtain a flexible thin fiber membrane absorbing material with good stability and excellent performance, we prepared a multi-layer hollow carbon sphere/CF@MoSe2 with carbon fiber as the matrix, and controlled the microstructure through hollow carbon shell and MoSe2, and introduced transition metal chalcogenides to coordinate electromagnetic parameters. As a result, the hollow carbon sphere/CF@MoSe2 flexible composite film achieved a minimum reflection loss (RLmin) of −47.98 dB at a thickness of 2.5 mm, and an effective bandwidth (EAB) of 8.1 GHz at a thickness of 2.7 mm. The RLmin of the hollow carbon ball/CF composite film reached −45 dB at a thickness of 2.6 mm, and the EAB reached 3.2 GHz. The theoretical characterization results jointly prove the reason for the improved performance, and this study provides an experimental basis for a more in-depth exploration of the birth of new absorbing materials.

Carbon Fiber Film with Multi-Hollow Channels to Expedite Oxygen Electrocatalytic Reaction Kinetics for Flexible Zn-Air Battery.

The high oxygen electrocatalytic overpotential of flexible cathodes due to sluggish reaction kinetics result in low energy conversion efficiency of wearable zinc-air batteries (ZABs). Herein, lignin, as a 3D flexible carbon-rich macromolecule, is employed for partial replacement of polyacrylonitrile and constructing flexible freestanding air electrodes (FFAEs) with large amount of mesopores and multi-hollow channels via electrospinning combined with annealing strategy. The presence of lignin with disordered structure decreases the graphitization of carbon fibers, increases the structural defects, and optimizes the pore structure, facilitating the enhancement of electron-transfer kinetics. This unique structure effectively improves the accessibility of graphitic-N/pyridinic-N with oxygen reduction reaction (ORR) activity and pyridinic-N with oxygen evolution reaction (OER) activity for FFAEs, accelerating the mass transfer process of oxygen-active species. The resulting N-doped hollow carbon fiber films (NHCFs) exhibit superior bifunctional ORR/OER performance with a low potential difference of only 0.60V. The rechargeable ZABs with NHCFs as metal-free cathodes possess a long-term cycling stability. Furthermore, the NHCFs can be used as FFAEs for flexible ZABs which have a high specific capacity and good cycling stability under different bending states. This work paves the way to design and produce highly active metal-free bifunctional FFAEs for electrochemical energy devices.

Hollow Fiber Carbon Molecular Sieve Membranes for Gas Separation: A Mini Review

Abstract: Owing to the advantages of rapid adsorption and desorption characteristics, excellent gas separation performance, as well as good thermal and chemical resistance, carbon molecular sieve (CMS) membranes have been developed as a promising gas separation tool. Over the past 30 years, hollow fiber carbon molecular sieve (HFCMS) membranes have become the preferred choice for industrial applications due to their high surface area-to-volume ratio and the ability to assemble lightweight membrane modules. The gas transport mechanism behind the HFCMS is dominated by molecular sieving function. They can be prepared by pyrolysis of the polymeric hollow fiber precursors. Post-treatments can tailor the ultramicropores structure to improve the separation performance. This paper aims to review the recent progress in the preparation of HFCMS membranes from aspects of precursor selection, pyrolysis conditions and post-treatment. Moreover, a brief perspective in terms of future investigation of HFCMS membrane is also proposed.

Preparation and sodium-ion storage performance of bimetallic oxygen sulfide composite hollow carbon fibers

Preparation and sodium-ion storage performance of bimetallic oxygen sulfide composite hollow carbon fibers

Hollow carbon fibers derived from biomass as enhanced anode materials for lithium- and potassium-ion batteries

Hollow carbon fibers derived from biomass as enhanced anode materials for lithium- and potassium-ion batteries

Enhanced electrochemical hydrogen storage performance of Co9S8 material by doping with cobalt nanoparticles embedded hollow porous carbon nanofibers

Co-axial electrospinning has been regarded as an effective technology to fabricate hollow or core/shell nanofibers. Herein, co-axial electrospinning was carried out employing polymethyl methacrylate (PMMA) and polyacrylonitrile (PAN) as the core and shell components. Cobalt acetate was used as the cobalt source. The cobalt nanoparticles embedded hollow porous carbon fibers (Co/HCNF) were obtained after electrospinning and subsequent carbonization process. For comparison, the conventional carbon fibers (CNF), hollow carbon fibers (HCNF), and cobalt nanoparticles modified carbon fibers (Co/CNF) were also synthesized. Co9S8 material was manufactured via mechanical alloying. By adjusting the types of carbon fibers, a series of carbon fibers modified Co9S8 composites were obtained by ball milling and their electrochemical hydrogen storage properties were studied. As a result, the Co9S8 + Co/HCNF electrode showed the higher discharge capacity of 603.3 mAh/g than CNF, HCNF, Co/CNF modified Co9S8 and conventional Co9S8 electrodes. The Co nanoparticles within Co/HCNF provided high electrocatalytic activity. The special hollow porous structure and high specific surface area of Co/HCNF increased the conductivity, offered more electrochemical active sites and rapid channel for charge transfer. Moreover, Co9S8 + Co/HCNF also demonstrated improved high-rate dischargeability (HRD), capacity retention and kinetics properties. An advantageous solid-solid interface may be generated between Co9S8 and Co/HCNF, serving as a beneficial electron conduction path and facilitating the hydrogen diffusion, thereby enhancing the electrode performance of Co9S8 material.